1. Field of the Invention.
The present invention relates to current drivers and, in particular, to an adaptive-output current driver.
2. Discussion of the Related Art.
A current driver is a circuit that sources current to and sinks current from a load so that the voltage across the load tracks the movement of an input voltage. Current drivers are commonly classified by the maximum mount of current that can be driven by the driver, and by the minimum mount of current, commonly known as the quiescent current, that will be consumed by the driver when there is little or no demand for current.
The maximum current that can be sourced by a driver is usually defined by the size of the output transistor which is sourcing the current. Thus, as the size of the output transistor increases, the maximum amount of current that can be sourced by the output transistor also increases.
The problem, however, is that the size of the output transistor also typically defines the minimum amount of current that will be consumed by the driver. Thus, as the size of the output transistor increases, the minimum amount of current that will be consumed by the driver also increases, thereby increasing the power consumed by the driver under quiescent conditions.
As a result, a typical current driver will have a relatively large quiescent current when the maximum demand for current is relatively high, as with an inductive load, and will only have a relatively small quiescent current when the maximum demand for current is relatively small. Thus, there is a need for a current driver which can quickly source a large current when there is a heavy demand for current, but which will also consume only a small quiescent current when there is little or no demand for current.